The present technique relates generally to a system and method of operating a compression-ignition engine and, more specifically, to a system and method for controlling peak cylinder pressure in a diesel engine operated at high altitude regions.
Compression-ignition engines, such as diesel engines, operate by directly injecting a fuel (e.g., diesel fuel) into compressed air in one or more piston-cylinder assemblies, such that the heat of the compressed air lights the fuel-air mixture. Compression-ignition engines also typically include a glow plug to provide heat to ensure ignition. The direct fuel injection atomizes the fuel into droplets, which evaporate and mix with the compressed air in the combustion chambers of the piston-cylinder assemblies. Typically, compression-ignition engines operate at a relatively higher compression ratio than spark ignition engines. The compression ratio directly affects the engine performance, efficiency, exhaust pollutants, and other engine characteristics. In addition, the fuel-air ratio affects engine performance, efficiency, exhaust pollutants, and other engine characteristics. Exhaust emissions generally include pollutants such as carbon oxides (e.g., carbon monoxide), nitrogen oxides (NOx), sulfur oxides (SOx), particulate matter (PM), and smoke. The amount and relative proportion of these pollutants varies according to the fuel-air mixture, compression ratio, injection timing, environmental conditions (e.g., atmospheric pressure, temperature, etc.), and so forth.
In certain applications, the compression-ignition engines are used in relatively extreme environmental conditions, such as high altitudes. For example, diesel powered locomotives can travel through a wide range of environmental conditions, particularly in mountainous regions. These environmental conditions can adversely affect engine performance, efficiency, exhaust pollutants, and other engine characteristics. For example, diesel engines operating in mountainous regions are subject to greater loads due to higher gradients, lower atmospheric pressures due to higher altitudes, lower temperatures due to colder climate or higher altitude, lower air density due to lower atmospheric pressure, and so forth. Fuel injection timing is advanced to improve engine efficiency. As a result, the peak in-cylinder pressure may rise to undesirable levels; emissions of pollutants may increase to unacceptable levels. The various engine parameters are particularly susceptible to exceed engine design limits when the engine is operating at a full load at extreme ambient temperature and altitude conditions. For example, an increase in peak in-cylinder pressure can be attributed to advance fuel injection timings, among other things. Unfortunately, existing engines do not adequately account for impact of advanced fuel injection timings on engine parameters, such as peak in-cylinder pressure.
Therefore, a technique is needed for controlling peak in-cylinder pressure for advanced fuel injection timing.